1. Field of the Invention
The present invention relates to an arrangement for reducing the moisture content of sludge.
2. Description of the Related Art
Sludge in the form of biological sludge is produced, inter alia, in the biological clarification of industrial waste waters, for example, the waste waters of a de-inking flotation plant. In the past, the biological sludge was usually considered a waste product and, therefore, was not utilized further. The sludge was deposited in dumps. However, since biological sludge has a very low dry substance content, it is very difficult to deposit the sludge and, therefore, the sludge has o be frequently mixed with other wastes having higher solids contents in order to be able to deposit the sludge in dumps. In addition to depositing the sludge in dumps, there is the transportation of the biological sludge to the dump which was always relatively expensive and cumbersome. It additionally significantly added to street traffic. Also, the dumping costs were extremely high, especially because less and less suitable dumping space can be made available. Moreover, the regulations concerning environmental protection with respect to the capability of dumping wastes become more stringent, so that the costs in this respect are also significantly increased.
Substantially the same problems occur in the case of industrial sludges in the form of, for example, oil sludge or solvent-containing sludges. In the case of these types of sludges, there is the additional disadvantage that they cannot be deposited in normal dumps, but must be brought to special dumps.